October 1816. John Keats is 20, working as a surgeon’s assistant at Guy’s. He goes to visit his friend, Charles Cowden Clarke – who has in his rooms early folio editions of the then neglected translations of the Iliadand Odyssey made by George Chapman (1559-1634). Keats knowsHomer only through Pope’s translation – which seemed then, as it does now, to pretty-up the raw rough power of the epics in a frill of politeness (despite Pope’s insight that Homer’s verses “pour along like a Fire that sweeps the whole Earth before it”). The friends spend the night plunging into Chapman’s verse, letting its cool, stimulating, unknowably vast expanse wash over them. Next morning, Keats writes his famous sonnet “On First Looking into Chapman’s Homer”. The night had made him feel “like some watcher of the skies / When a new planet swims into his ken”. It was an epiphany, and a crucial moment in Keats’s self-realisation as a poet.

My Homeric epiphany came seven summers ago, on a road trip to Cornwall, reading Robert Fagles’s translation aloud and having it read to me over the immense chugging of an old camper van’s engine, and then at night, by the light of an oil lamp. Like Adam Nicolson, I had read it in Greek when young, teasing out the sense like “picking bones from fish”, a lovely image that the author of the Odyssey – but not the Iliad – might have used. I’d never got the sweep and the scale, though: the way the Iliadcarries you through death and death and death, thousands of lines of horror and human pity, andthen turns on the colour, the special effects, the all-day permanent red (to steal a phrase fromChristopher Logue) when Achilles, that tender-hearted, grim-hearted killing machine, embarks on his grief-fuelled rampage. I think I needed Homer to be relieved of the dictionary, to be remade as a story told aloud by the light of a flickering flame.

Nicolson’s epiphany came as he sailed his boat up the west coast of Ireland – a latter-day Odysseus battling the ferocious and unharvestable sea. There is a literal recognition here: Odysseus, that most salt-caked of ancient heroes, is surely a companion to anyone who has felt the exhilarating terrors of steering a boat under sail at night. But there is also a metaphorical recognition: he begins to see the Odyssey as a poem about the journey through the uncharted waters of one’s life. It became a kind of scripture to him: “as the Odyssey knows, to live well in the world … you must stay with your ship, stay tied to the present, remain mobile, keep adjusting the rig, work with the swells, watch for a wind-shift, watch as the boom swings over, engage, in other words, with the muddle and duplicity and difficulty of life.” Nicolson had had a Keatsian moment of revelation that the Odyssey was telling him “the unaffected truth … speaking about fate and the human condition in ways that other people only seem to approach obliquely”. I agree. When I listen to Radio 4 and think about my own Desert Island book, it’s obvious to me that, along with Shakespeare and the Bible, it would be Homer, because all that is human is in the lines of these poems. Plus, the Odyssey contains detailed instructions on how to construct an escape raft.